1. Field of the Invention
The present invention relates, in general, to tapping machines and, more particularly, to a horizontal cutting type tapping machine, allowing the saw part of the machine to be positioned close to a main pipeline, thereby effectively cutting an opening of a large diameter in a main pipeline.
2. Description of the Prior Art
In order to supply fluid, such as gas, water and water drainage from a source to a necessary location, supply pipelines are laid underground.
Supply pipelines for supplying a fluid from a source to a desired location comprise a main pipeline for supplying the fluid from a source to a place adjacent to the necessary location, a branch pipeline for supplying fluid from the main pipeline to the desired location, and a connecting pipe for connecting the main pipeline to the branch pipeline.
Referring to FIGS. 1 and 2, a process for installing the supply pipelines underground is performed by laying a main pipeline 1 underground, laying a branch pipeline 2 so that its one end is positioned over the main pipeline 1, connecting the main pipeline 1 to the end of the branch pipeline 2 by means of a vertical connecting pipe 3 having a flange 3a at its top, cutting an opening in the wall of the main pipe 1 by means of a horizontal cutting type-tapping machine, engaging a plug 4 with the flange 3a, and fixing a lid 5 to the flange 3a with bolts.
Incidentally, a specific technology is required for preventing leakage of the fluid during installation of the connecting pipe 3. On the other hand, since such technology is well known and is described in Korea patent No. 202503 granted to the instant applicant, the detailed description of the technology is omitted in this specification.
However, a pipe connecting structure of this type has problems in that the structure is subjected to load and vibration from the ground and becomes exposed (positioned outside the ground) because the branch pipeline 2 is disposed at a position above the main pipeline 1, thereby being easily damaged.
The underground-laying depths are usually prescribed by law. In Korea, the depth for laying supply pipelines under a road wider than 8 m is 1.2 m, the depth for laying supply pipelines under a road of less than 8 m width is 1.0 m, and the depth for laying supply pipelines in a residential district is 0.6 m.
As shown in FIG. 2, the supply pipelines are laid under a base layer and a surface layer, the base layer consisting of sand and pebbles, the surface layer being made of asphalt.
The main pipeline 1 and the branch pipeline 2 are preferably laid underground at the same depth, but the branch pipeline 2 has been disposed at a position above the main pipeline 1 because the connecting pipe 3 has to be vertically mounted and the main pipeline 1 must have an opening in its top portion.
The applicant of this invention holds Korea patent No. 202503, in which, in order to solve the abovementioned problems, the main pipeline and the branch pipeline are laid underground at the same depth and are connected by means of a horizontal connecting pipe (see FIGS. 3 and 4).
In such a case, a tapping machine for cutting an opening in the side of the main pipeline 1 comprises a main body 6 of the machine. A shut-off valve 9 is mounted under the main body 6.
A cutting head 7 is rotatably connected to the main body 6 through the extended drive shaft of the main body 6. A saw part 8 is fixed to the end of the horizontal rotating shaft of the cutting head 7.
In use of the tapping machine, the cutting head 7 is lowered to face the wall of the main pipeline 1, the horizontal rotating shaft of the cutting head 7 is moved forward, the drive shaft of the main body 6 is rotated so as to rotate the horizontal rotating shaft of the cutting head 7 and the saw part 8 is rotated by the rotation of the rotation shaft. Accordingly, an opening is cut in the side of the main pipeline by the rotation of the saw part 8.
However, according to the conventional horizontal cutting type-tapping machine, the saw part of the machine may not be positioned close to a main pipeline because the saw part is not able to be bent. As a result, effectively cutting an opening of a large diameter in a main pipeline is difficult.